thanks Dutch and pbman.
I managed to fix my laptop last night - at first I tried booting from an external hard drive but for some reason I didn't have much luck.
So then I went into the recovery console and typed 'chkdsk /p' which did a search through the drive and when that was done I typed 'fixboot' which seemed to fix the problem.
XP booted normally and all of my work was fine so I quickly made some back ups. Just wish I hadn't waited so long to try a repair.
Here are a couple of links which deal with the error: 'Unmountable Boot Volume'.
sorry to hear that you are having some problems pbman. Hope you manage to sort it out.